A pixel includes a photodiode and a readout node for receiving charge transferred from the photodiode. The readout node is configured to have a variable capacitance that is non-linear with respect to a voltage at the readout node. The readout node is resettable. The readout node may be configured to have a lower capacitance when reset to a reset voltage than when getting filled with charge from the photodiode. The readout node may be configured such that the capacitance of the readout node continuously increases as additional charge is received by the readout node after the readout node is reset. The readout node may be configured such that the capacitance of the readout node jumps from a first capacitance to a second capacitance after the readout node has been filled with a certain amount of charge. An image sensor includes a pixel array with a plurality of the pixels.